Help Needed with Twitchy Quad: FIXED

[eyeflying]

Just built this quad on a 450 frame with a MultiWii board but got a problem which I hope someone can help with.

The quad seems to fly fine but then starts twitching and will suddenly drop (or flip - see vid). I';ve played with the PID';s, changed the board for another identical board (same problem though). I put the board in another quad - Turnigy HAL - and it flies fine.

This is starting to look like a hradware issue to me?? - Any advice before I just it as a leaf blower 

http://youtu.be/g4FghZ70ePE

[Gaza07]

Cant really tell in the video if its the same motor stopping each time, could it be a dodgy esc or motors, is the cut off disabled in all the esc';s
Hold the quad out at arms length with a bit of throttle and rock it to make the motors work and see if the same one packs up all the time, if it does change the esc and test again if its not cured try changing the motor, its just a process of elimination 

[eyeflying]

Hmmm... It does seem like a dodgy motor or ESC. I';ve fitted one of those Skywalker Quattro ESC';s (4 in 1) - never tried this before. I';ll do what you suggest and keep you posted on the result

[eyeflying]

Fixed the ';twitch and drop'; problem.

There were 3 problems with the setup - all software related. Firstly I modified the Yaw PID';s to a really low value P=3. Then lowered the Gyros Lo Pass Filter. Then isolated the control board to reduce vibration.

The quad now seems really stable but probably still needs a couple of minor tweaks to get it perfect.

Frustration over 

[Gaza07]

Glad to hear you got t sorted and thanks for posting what the problem was it could help some one else at some point